The present invention is concerned with the bulking of linear polycarbonamide fibers.
The fibers with which the invention is concerned are silk-like linear, high molecular weight polyamide fibers wherein at least 90% of the repeating units have the formula ##STR1## wherein S indicates a saturated cyclohexyl ring and the R substituents, which may be the same or different, are selected from the group consisting of hydrogen and methyl. At least 40% by weight of the diamine constituent of the repeating unit is of the trans-trans (t) sterioisomeric configuration.
Fibers of the above type, and fabric made therefrom, are described in U.S. Pat. No. 3,393,210, the subject matter of which is incorporated herein. Typically, the fibers are made from the polyamide polycondensate of 4,4'-diaminodicyclohexylmethane with dodecanedioic acid. Such material is commercially available (Dupont) depending on finish, denier, etc., as Nylon Types 470, 472, 473 (trademarked as "Qiana"). The latter material has a silk-like handle, a density of 1.04, and a crystallinity similar to polyester fibers as reported by A. Liddiard, Review of Progress in Coloration, Vol. 1, page 64, June '67-September '69.
It is disclosed in DuPont's bulletin on Preparation, Dyeing and Finishing Woven and Warp Knit Fabrics of Type 470, Type 472, and/or T-473 Nylon Filament Yarns, that these fabrics can be thermally bulked and stabilized in the greige state or after being scoured and dried, either on an externally taperable pin tenter frame, or on a rational hot roll contact unit, or similar type machines. However, heat bulking as such tends to yellow the "Qiana", renders it more difficult to dye, and does not help develop the silk-like handle of the fabric to its fullest degree.
The principal object of the present invention is to provide a process for bulking fabrics made from fibers of the type indicated above (Type 470, Type 472 and/or Type 473 Nylon filament yarn "Qiana") which obviates prior art problems and positively develops the silk-like handle of these fabrics to their fullest degree and renders them easier to dye, with a minimum of adverse modification of the fibers.
Other objects will also be apparent from the following more detailed description of the invention.